INTEGRAL observations of IGR J11215-5952: the first Supergiant Fast X-ray Transient displaying periodic outbursts
Abstract
The hard X-ray source IGR J11215-5952, discovered with INTEGRAL during a brief outburst in 2005, has been proposed as a new member of the class of Supergiant Fast X-ray Transients. Analysing archival INTEGRAL observations of the source field, we have discovered two previously unnoticed outbursts (in July 2003 and in May 2004), spaced by intervals of ~330 days, suggesting a possible orbital period. The 5-100 keV spectrum is well described by a cut-off power law, with a photon index of ~0.5, and a cut-off energy ~15-20 keV, typical of High Mass X-ray Binaries containing a neutron star. The luminosity is ~3 × 1036 erg s-1 assuming 6.2 kpc, the distance of the likely optical counterpart, the blue supergiant HD 306414. A fourth outburst was discovered in 2006 with XTE/PCA, 329 days after the third one, confirming the periodic nature of the source outbursts. Follow-up observations with Swift/XRT refined the source position and confirmed the association with HD 306414. The 5-100 keV spectrum, the recurrent nature of the outbursts, the blue supergiant companion star HD 306414, support the hypothesis that IGR J11215-5952 is a Supergiant Fast X-ray Transient, and it is the first object of this class of High Mass X-ray Binaries displaying periodic outbursts.
- Publication:
-
The Multicolored Landscape of Compact Objects and Their Explosive Origins
- Pub Date:
- August 2007
- DOI:
- 10.1063/1.2774902
- arXiv:
- arXiv:astro-ph/0610890
- Bibcode:
- 2007AIPC..924..508S
- Keywords:
-
- 98.70.Qy;
- 97.80.Jp;
- 97.20.Pm;
- 97.60.Jd;
- X-ray sources;
- X-ray bursts;
- X-ray binaries;
- Supergiant stars;
- Neutron stars;
- Astrophysics
- E-Print:
- To be published in the proceedings of the conference "The Multicoloured Landscape of Compact Objects and their Explosive Origins", eds.L.Burderi et al., held in Cefalu', Sicily (Italy), June 11-24, 2006. Submitted